Earthquake-triggered giant tsunamis can cause catastrophic disasters to coastal populations, ecosystems and infrastructure on scales over 1000s km. In particular, the scale and tragedy of the 2004 Indian Ocean (about 230,000 fatalities) and 2011 Japan (22,000 fatalities) tsunamis prompted global action to mitigate the impacts of future disasters. In this Review, we summarize the progress in understanding tsunami generation, propagation, and monitoring, with a particular focus on developments in rapid early warning and long-term hazard assessment. Dense arrays of ocean-bottom pressure gauges in offshore regions provide real-time data of incoming tsunami wave heights, which combined with advances in numerical and analog modeling, have enabled the development of rapid tsunami forecasts for near-shore regions (within 3 minutes of an earthquake in Japan). Such early warning is essential to give local communities time to evacuate and save lives. However, long-term assessments and mitigation of tsunami risk from probabilistic tsunami hazard analysis (PTHA) are also needed so that comprehensive disaster prevention planning and structural tsunami countermeasures can be implemented by governments, authorities, and local populations. Future work should focus on improving tsunami inundation, damage risk, evacuation modeling and reducing the uncertainties of PTHA associated with the unpredictable nature of megathrust earthquake occurrence and rupture characteristics.
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